linux-kernel - Re: [PATCH v4 2/6] power: add power sequence library

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Date:	Wed, 3 Aug 2016 15:16:58 -0700
From:	Matthias Kaehlcke <mka@...omium.org>
To:	Peter Chen <peter.chen@....com>
Cc:	gregkh@...uxfoundation.org, stern@...land.harvard.edu,
	ulf.hansson@...aro.org, broonie@...nel.org, sre@...nel.org,
	robh+dt@...nel.org, shawnguo@...nel.org, dbaryshkov@...il.com,
	dwmw3@...radead.org, k.kozlowski@...sung.com,
	linux-arm-kernel@...ts.infradead.org, p.zabel@...gutronix.de,
	devicetree@...r.kernel.org, pawel.moll@....com,
	mark.rutland@....com, linux-usb@...r.kernel.org, arnd@...db.de,
	s.hauer@...gutronix.de, mail@...iej.szmigiero.name,
	troy.kisky@...ndarydevices.com, festevam@...il.com,
	oscar@...andei.net, stephen.boyd@...aro.org,
	linux-pm@...r.kernel.org, stillcompiling@...il.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 2/6] power: add power sequence library

El Tue, Aug 02, 2016 at 11:30:48AM +0800 Peter Chen ha dit:

> diff --git a/drivers/power/pwrseq/core.c b/drivers/power/pwrseq/core.c
>
> ...
>
> +static DEFINE_MUTEX(pwrseq_list_mutex);
> +static LIST_HEAD(pwrseq_list);
> +
> +int pwrseq_get(struct device_node *np, struct pwrseq *p)
> +{
> +	if (p && p->get)
> +		return p->get(np, p);
> +
> +	return -ENOTSUPP;
> +}
> +
> +int pwrseq_on(struct device_node *np, struct pwrseq *p)
> +{
> +	if (p && p->on)
> +		return p->on(np, p);
> +
> +	return -ENOTSUPP;
> +}
> +
> +void pwrseq_off(struct pwrseq *p)
> +{
> +	if (p && p->off)
> +		p->off(p);
> +}
> +
> +void pwrseq_put(struct pwrseq *p)
> +{
> +	if (p && p->put)
> +		p->put(p);
> +}
> +
> +void pwrseq_free(struct pwrseq *p)
> +{
> +	if (p && p->free)
> +		p->free(p);
> +}
> +
> +void pwrseq_register(struct pwrseq *pwrseq)
> +{
> +	mutex_lock(&pwrseq_list_mutex);
> +	list_add(&pwrseq->node, &pwrseq_list);
> +	mutex_unlock(&pwrseq_list_mutex);
> +}
> +
> +void pwrseq_unregister(struct pwrseq *pwrseq)
> +{
> +	mutex_lock(&pwrseq_list_mutex);
> +	list_del(&pwrseq->node);
> +	mutex_unlock(&pwrseq_list_mutex);
> +}

What is the purpose of pwrseq_register/unregister()? The pwrseq
structs are added and removed from pwrseq_list, but besides that
pwrseq_list is not used.

Looks like this is a remainder from the ancestor of this code
(drivers/mmc/core/pwrseq.c) which uses the list to avoid having
multiple pwrseq instances for the same device.

Matthias